problem with vintage oil furnace starting

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I have an oil furnace, forced air, It's a Carrier 58HV085, 34 years old, and works well, until last night after I fell asleep.
(Please, no one tell me to get a new furnace. I've heard that before. When I can, I will.)
I woke up early and the 2nd floor temp was 60 instead of 68.
Question 1: When the thermostat is set to auto, as it always is, the air circulation fan goes on about a minute after the furnace starts. In a furnace of this age, is that because of the Fan and Limit Control???? As opposed to something on the small control board, which has only about 15 resistors, capacitors, transistors, including 2 relays.
Question 2: Does the Fan and Limit Control keep the furnace running once it reaches fan termperature (and until the thermostat says for it to stop.)? I would think the answer is No, and that the control board alone starts the furnace and keeps it running, until the thermostat says no.
To try to get the furnace going, I pressed the reset button, but it didn't need to be reset. I checked the circuit breaker; measured the voltage on the secondary of the power transformer, and removed the control box cover, just in case anything cried out, "I'm broken".
Besides the relay with the reset button, there is another relay next to it, about 3/4" cubed. I pressed the armature down and the furnace started. Let go after 3 seconds and it stopped.
Thought about checking out the thermostat, but didn't know what color wires were used for heat. Thought about replacing the whole control circuit board, but figured I'd better test the thermostat first.
To get some heat until I could learn wire colors and maybe replace the thermostat, thought I'd jam a piece of wood between the relay armature and something above it. Didn't find the right length of wood, but even a shorter piece was heavy enough to hold down the armature, just leaning against the cabinet.
That started the furnace and immediately I thought, "Will the house fan start? Can't run the furnace for long without the fan" Ran for about 3 minutes but didn't hear the fan start, so I removed the piece of wood. Furnace is still running!!!. Does the Fan and Limit Control on a 34 yo Carrier keep the furnace running once it gets hot enough but the thermostat hasn't said Stop yet?? I thought not, but the furnace is still running. If the answer really is NO, something has changed since the furnace didn't run all night.
I had to leave the furnace room to find an air vent, and indeed, the fan is blowing.
I'm 99% sure it will turn off when the house is warm, but not at all sure it will restart when it should.
Any suggestions, other than getting a new furnace?
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On 02/11/2014 06:56 AM, micky wrote:

I'm sure it's fixable but really
why don't you get a high efficiency gas furnace?
When I got rid of my oil burner and went to gas I saved so much money it was well worth it.
It paid for itself within two years.
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On Tuesday, February 11, 2014 7:58:44 AM UTC-6, philo  wrote: philo, the key here is:

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On 02/11/2014 08:02 AM, Bob_Villa wrote:

He can do it today
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On 2/11/2014 7:56 AM, micky wrote:

SM: Night, colder, furnace works harder.

SM: Can be either.

SM: No, typically not.

SM: Amazing, what you can find with a good look see.

SM: Blower fan, or burner assembly started?

SM: No sense throwing parts at it.

SM: Started the furnace. You mean the burner gun, or the air handler blower? I guess if the fan didn't start, which fan was that? The air handler fan?
Does the Fan and Limit Control on a 34 yo

SM: Typically the fan limit does two things. Turns the air handler fan on when the fire box is hot. turns the burner off, if the firebox is too hot.
I thought not, but the furnace is

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On Tue, 11 Feb 2014 09:31:23 -0500, Stormin Mormon

Only the oil pump and the fan on the same motor started, and the ignition. That's all that normally starts. Later, the big air fan turns on.

I hate that term "air handler". What did they call it before air conditioning? But yeah, that's what I was referring to but it did start. I just didn't hear it.

I guess I thought about the second but not about the first, until today.
Thanks.
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On 2/11/2014 1:19 PM, micky wrote:

My pleasure. BTW, did you get it repaired?
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On Tuesday, February 11, 2014 7:56:18 AM UTC-5, micky wrote:

In the old ones I've seen, yes. Temp switch in the plenum turns on the fan when it gets hot, shuts it off when it gets cool.

I'd say that's kind of right. The limit switch does form part of the circuit that keeps it running though. If the temp gets too high, it shuts it down.

Red is power, white is heat, yellow is AC, green is fan. That's the usual convention. So for heat, connect red to white.
Thought about replacing the whole control

Without knowing exactly what that relay button bypasses, I sure wouldn't jamb it closed with a stick.

Find a schematic that shows the controls, how they are wired, and proceed with the debugging. Or call for service.
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On Tue, 11 Feb 2014 06:43:04 -0800 (PST), " snipped-for-privacy@optonline.net"

Makes sense now. Where else would it be? But I just figured it was a mystery box.

When I counted, my imagination was way off. There were only 2 resistors, 1 capacitor, 2 transistors, and 2 relays. ....

Thanks. That helps.

minutes, to keep the firebox from overheating, but (it stayed on and) when I went to a quieter room, I could hear the "air handler" blowing and next I found a a vent within reach where I could feel the air blowing.

It didn't.

The manual I found online has been good for specs, but the schematic has too many discrepancies from my furnace, even though it's the same model number. The one online is probably the final schematic and mine wasn't. I see that in tvs too. I'll look for my paper copy that actually came with the furnace.
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wrote:

closed, but not be able to PULL it closed. Check the relay coil. Also check the control transformer voltage. If it is supposed to be 24 and it is only 16, the reays are not going to function properly. Also check the wires for high resistance.
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On Tue, 11 Feb 2014 19:03:04 -0500, snipped-for-privacy@snyder.on.ca wrote:

Will do.
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On Tue, 11 Feb 2014 19:03:04 -0500, snipped-for-privacy@snyder.on.ca wrote:

Will do.
BTW, in the original thermostat, a round Honeywell that was so popular for so long in the 60's and 70's (not the one I'm using now,) there were some square sine waves circuit traces on the little round circuit board, and I see something on the heating cooling wiring schematic that seems to correspond.
On the schematic they are labeled HTG ANT and CLG ANT.
Do you all know anythihng about these?
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wrote:

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On Sat, 15 Feb 2014 22:15:48 -0500, snipped-for-privacy@snyder.on.ca wrote:

Ah. I thought they were heating antenna and cooling antenna. Your answer makes a lot more sense.
P&M because it's been two days and the group is busy.
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On 2/15/2014 9:05 PM, micky wrote:

I've got a pretty good guess. I've had to set the old rounds, and yes, pretty sure I know.
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Micky,
Do you have a circuit diagram? Have you checked the relay that is no longer closing? Is there power to the relay? Is the coil of the relay fried?
Dave M. ce?
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On Tue, 11 Feb 2014 10:36:16 -0500, "David L. Martel"

I'd forgotten that the owners manual included a both a wiring schematic and a wiring diagram, they call them. The second is laid out more like in real life, with things that are physically close being close on the diagram.
The diagram is hard for me to understand because I'm used to pure electronics diagrams. Or maybe it's because they updated things before ending this model. I got this off the web, but I need to find the paper manual that came with the furnace, which will match the furnace exactly.
(For example, the online disagram shows things running off the center tap of the secondary, but when I had to replace the transformer 30 years ago, nothing was connected to the center tap. The online manual shows a solid state switch, intead of two mechanical relays. It shows no reset button (which is mechanical, not electric exactly, but would still be indicated if they were still using one.
(It shows that the air fan is on high for AC and one of three setting for heat, but mine uses the same speed for AC and heat, I'm 99% sure.
(The online manual seems to indicate one resistor, marked 1K, but it also shows a set of contact poitns or a capacitor marked 1K2 !! 1K and 1K2 might be the missing relay, but I really need to find my paper owners manual.

I havent' checked that. Good point. Probably not.

I doubt it because the armature stayed down after I held it down for a couple minutes. And the furnace turned off when the second floor temp was 66, so after another test, I pushed the armature down again, (maybe on the right side instead of the left and probably farther than the first time, when it was just 3 seconds) and this time I heard it click, like the armature hitting the coil, and it stayed down from the beginning. So I think that's the coil holding it in.
(Hmm. The furnace just stopped. Upstairs temp is just 70 degrees (It's usually warmer than the first floor. ))
The test I made was jumping the thermostat connections at the furnace and that didn't start it up. I think that means the thermostat is okay, Or at least there is a problem with the control board, but to be sure I want to disconnect the stat and measure the resistance between those wires when the house is warm and when it is cold. Can't do it when the thermostat's connected because there are 24 volts between those wires/screws.
If it's not the thermostat, it's the control board, and I have a spare one from the identical burner a neighbor replaced. (Well I think it's identical. When I take the cover off the control board, it might match the online wiring diagram.)
Since the current control board has only 2 resistors, one capacitor, 2 transistors, and 2 relays, maybe I could fix it, but exchanging it is easier. Maybe I'll try to fix the old one then.

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On 2/11/2014 7:56 AM, micky wrote:

Since you forced the burner on, but the air handler blower didn't come on, makes me wonder if the fan limit switch is open, and reading high temp overlimit?
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On Tue, 11 Feb 2014 10:51:35 -0500, Stormin Mormon

No, it did come on. See my two line paragraph above. I didn't *hear* it come on when I was standing right next to the furnace. Too much noise there.

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On 2/11/2014 1:14 PM, micky wrote:

Ah, that makes more sense. Thanks.
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